Nine Quick and Easy Light Experiments to Share with Your Kids

Nine Quick and Easy

Light Experiments

to Share with Your Kids

By Aurora Lipper

Can you make the color 'yellow' with only red, green, and blue as

your color palette? If you're a scientist, it's not a problem. But if you're

an artist, you're in trouble already.

The key is that we would be mixing light, not paint. Mixing the three

primary colors of light gives white light. If you took three light bulbs (red,

green, and blue) and shined them on the ceiling, you'd see white. And if

you could un-mix the white colors, you'd get the rainbow. That's what

prisms do.

If you're thinking yellow should be a primary color - it is a primary

color, but only in the artist's world. Yellow paint is a primary color for

painters, but yellow light is actually made from red and green light.

Confused? Good, because we're going to spin colors, mix and un-mix colors,

and play with the electromagnetic spectrum. Let's get started.

Mixing Colors Find three flashlights. Cover each with colored cellophane or

paint the plastic lens cover with nail polish (red, green, and blue). Shine

onto a white ceiling or wall, overlap the colors and make new colors. Leave

the flashlights on, line them up on a table, turn off the lights, and dance you will be making rainbow shadows on the wall! In addition, you can paint

the lens of a fourth flashlight yellow.

More About Mixing Colors When you combine red and green light, you will

get yellow light. Combine green and blue to get cyan (turquoise). Combine

blue and red to get magenta (purple). Turn on the red and green lights, and

the wall will appear yellow. Wave your hand in front of the lights and you

will see cyan and magenta shadows. Turn on the green and blue lights, and

the wall turns cyan with yellow and magenta shadows. Turning on the blue

and red give a magenta wall with yellow and cyan shadows. Turn on all

colors and you will get a white wall with cyan, yellow, and magenta shadows

¨C rainbow shadows!

Spectrometer Find an old CD and a cardboard tube at least 10 inches long.

Cut a clean slit less than 1 mm wide in an index card or spare piece of

cardboard and tape it one end of the tube. Align your tube with the slit

horizontal, and on the top of the tube at the far end cut a viewing slot about

one inch long and ?¡± inch wide. Cut a second slot into the tube at a 45o

from the vertical away from the viewing slot. Insert the CD into this slot so

that it reflects light coming through the slit into your eye (viewing slot). Aim

the 1 mm slit at a light source (such as a fluorescent light, neon sign,

sunset, light bulb, computer screen, television, night light, candle, fireplace¡­

any light source you can find. Look through the open hole at the light

reflected off the compact disk (look for a rainbow in most cases) inside the

cardboard tube.

Pinhole Camera Use a cardboard box that is light-proof (no leaks of light

anywhere). Cut off one side of the box (there's no need to do this if you're

using a shoebox). Tape a piece of tracing paper over the cutout side,

keeping it taut and smooth. Make a pinhole in the side opposite the tracing

paper. Point the pinhole at a window and move toward or away from the

window until you see its image in clear focus on the tracing paper. You can

hold up a magnifying glass in front of the pinhole to sharpen an image.

Kaleidoscopes Carefully tape together three identical mirrors, making a

triangle-tube with the mirrors on the inside. (You can also use Mylar or

silver wrapping paper taped to cardboard instead of mirrors.) Tape all rough

edges well and peek through the opening as you walk around.

Kaleidoscope Variations By changing the size and shape of the mirrors,

you can change the dimensional effect you see. Just be sure to look at the

mirror surface, not the opening. Variations include: make mirrors wider at

the bottom and narrower at the top (easier with cardboard mirrors); use

four or five mirrors instead of three; change the length of the mirrors; use

curved mirrors instead of flat (find curved cardboard from an oatmeal box or

carefully cut apart a soda can and tape Mylar or spray with chrome paint

from the hardware store).

Telescopes and Microscopes Hold one magnifying glass in each hand.

Focus one lens on a printed letter or small object. Add the second lens

above the first, so you can see through both. Move the lens toward and

away from you until you bring the letter into clear focus again. You just

made a microscope! The lens closest to your eye is the EYEpiece. The lens

closest to the object is the OBJECTive. Now focus on a far-away object like

a tree. You just made a simple telescope¡­ but the image is upside-down!

Homemade Diffraction Take a feather and put it over an eye. Stare at a

light bulb or a lit candle. You should see two or three flames and a rainbow

X. Shine a flashlight on a CD and watch for rainbows.

Spinning Colors There are three primary colors of light: red, green, and

blue (artists use red, yellow, and blue). Use a cup to outline circles on a

sheet of stiff white paper (or manila folders). Stack several blank pages

together and cut out multiple circles. Color the circles, push a sharp wooden

pencil through a hole in the center, and spin! What color does yellow and

blue make? Pink and purple? You can also make a button-spinner to really

whirl it around by looping a length of string through two holes in the center

of the disk circle.

Water Prism Set a tray of water in sunlight. Lean a mirror against an

inside edge and adjust so that a rainbow appears on the wall. You can also

use a light bulb shining through a slit in a flat cardboard piece as a light

source.

Polarization If you have polarizer filters, use two of them. You can

substitute two sunglass lenses (no need to pop out the lenses) using two

pairs of good sunglasses. Make sure your sunglasses are polarized lenses

(most UV sunglasses are). Look through both lenses, then rotate one pair

90o. The lenses should block the light completely at 90o and allow light to

pass-through when aligned at 0o. Think of your sunglasses as light filters.

They allow some light to pass through but not all. When you rotate the

lenses to 90o, you block out all visible light.

More About Polarization You use the filter principle in the kitchen. When

you cook pasta, you use a filter (a strainer) to get the pasta out of the

water. That's what the sunglasses are doing ¨C they are filtering out certain

types of light. Rotating the lenses 90o to block out all light is like trying to

strain your pasta with a mixing bowl. You don't allow anything to pass

through. You can make sunglasses tinted darker or lighter by adjusting the

amount of rotation between the two lenses before you glue them together

into one lens. Astronomers use polarizing filters to look at the moon. Ever

notice how bright the moon is during a full moon, and how dim it is near

new moon? Using a rotating polarizing filter, astronomer can adjust the

amount of light that enters into their eye.

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